This invention relates to a method of creating NC data in an automatic programming apparatus and, more particularly, to an NC data creation method so adapted that a tool can be made to avoid striking an obstacle if one is present on a tool travel path generated in accordance with a predetermined rule.
There are cases where a tool, after completing the machining of a first area, is moved to a second area to subsequently perform predetermined machining at the second area. For example, as shown in FIG. 5(A), there are cases where hole machining of a prescribed type is performed at a first area AR1, after which the tool used at the first area AR1 is moved as is (i.e. without being exchanged for another) to a second area AR2, where hole machining of another type is then carried out. In such cases, the tool must be moved from the first area AR1 to the second area AR2. In the prior art, this is accomplished by previously deciding the position of an approach surface APS in the height direction (Z direction), retracting the tool to the approach surface APS after is has completed cutting a final hole H12 at the first area AR1, thenceforth moving the tool on the approach surface to a point directly above an initial hole H21 at the second area AR2, then causing the tool to approach the initial hole and subsequently cutting a hole at the second area. In FIG. 5(A), WK represents the workpiece in which the holes are formed, H11, H12 . . . denote the holes in the first area AR1, and H21, H22 . . . denote the holes in the second area.
There are situations where an obstacle is present on the tool travel path between the first area AR1 and second area AR2. For example, as shown in FIG. 5(B), a portion of the workpiece WK may protrude beyond the approach surface APS between the first area AR1 and second area AR2. If the tool path is decided in accordance with the conventional method in such situations, the tool will strike the protuberance when it attempts to move from the first area AR1 to the second area AR2.